Telephone-exchange system



G. THOMPSON. TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED AuGJ. 1919.

1,383,677. Patented July 5, 1921.

lfl lf van/0r George Thompson y [My UNITED STATES PATENT OFFICE.

GEORGE THOMPSON, OF MOUTIT VERNON. NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORA- TION OF NEW YORK.

TELEPHONE-CHANGE SYSTEM.

Specification of Letters Patent.

Application filed August '7, 1919. Serial No. 315,820.

' Mount Vernon, in the county of estchester,

receiving a variety of expressions, one of State of New York, ,have invented certain new and useful Improvements in Telephone- Exchange Systems, of which the following is a full, clear. concise, and exact description.

This invention relates toiinprovements in telephone exchange systems ,and has particular reference to a circuit arrangement for line switches.

An object of the invention is to cause a line switch to test for an idle trunk by means of the stepping magnet of said switch.

In accordance with this object, the stepping magnet is preferably provided with a differential winding which permits the magnet to operate the switch over terminals of busy trunks. but which prevents further operation of said magnet when the brushes of the switch engage the-terminals of an idle trunk.

The inventive idea involved is capable of which, for the purpose of illustrating the invention, is shown in the accompanying drawing; but it is to be expressly understood that said drawing is employed merely for the purpose of facilitating the description of the invention as a whole and not to define the limits thereof, reference being made to the appended claims for this purpose.

The drawing illustrates diagrammatically a circuit arrangement employed in carrying out the invention.

It is believed that the invention will be fully understood from the following detailed description of the operation.

Vhen a subscriber at substation 1 mitiates a call by removing his receiver from its switchhook, a circuit is closed for line relay 2 of the line switch extending from grounded battery, left winding of said relay, back contact and inner upper armature of cut-oft relaytl, substation apparatus 1, outer upper armature and back contact of relay 3. and right winding of relay 2, .to ground. By attracting its outer armature, relay 2 establishes a self-interrupting circuit for differential stepping magnet 4 extending from grounded battery, lower at mature and back contact of cut-off relay 3,

front contact and outer armature of relay 2, right-winding, armature and back contact of magnet 4, to ground. Magnet 4 is energized and, preferably upon the back stroke,,operates to step the brushes of the' switch from the normal terminals on to the first set of terminals to which a trunk is con.- nected leading to a selector switch of any well-known construction. When brush 5 engages the contact bar 6 upon (ihe first step of the switch, battery is applie to the conductor 7 through said brush which will pro vide a busy test for substation 1 should a final connector be set u 3011 the multi 1e contacts individual to said substation. Jngagement of brush 8 with contact bar 9 establishes another self-interrupting circuit for stepping magnet 4 independent of the outer armature of line relay 2, so that should the subscriber at substation 1 replace his receiver upon the switchhook and thus den- 'ergize the line relay, stepping magnet/i Will continue to operate the switch over the ter minals of all trunks until the same is returned to its normal position. If the first trunk leading to a succeeding selector switch is busy, a relay of said se lector switch, similar to relay 10, and the cut-off relay of the busy line switch will both be energized. Energization of the relay similar to relay 1.0 will remove battery from its armature and back contact and thus prevent the closing of a circuit through the left differential winding of ma net 4. The ground at the cut-off relay of t e busy line switch will be applied to the busy test terminal and thus shunt the cut-off relay 3. The stepping magnet 4 will therefore continue to operate and step the brushes of the switch over the terminals of all busy trunks until an idle trunk is found. At this time the engagement of brush 11 with itsassociated terminal immediately closes the above-mentioned circuit through the left differential winding of magnet 4 which circuit is traceable from grounded battery, back contact and armature of uelay '10 at the selecto switch, this relay being deenergized, brush 11, front contact and inner armature of relay 2 and left winding of magnet 4, to ground. tial winding of said magnet in conjunction with the circuit through the right winding thereof, will operate to prevent further ener- Patented July 5, 1921.

This circuit through the diifereni gization of the magnet and thus bring the switch to rest upon the terminals of the idle trunk. It will be noted that the closure of the last mentioned circuit will also momentarily establish a circuit to ground through the winding of the register magnet 12, but this magnet is adjusted so as not to operate on the battery potential of relay 10. St multaneously with the closure of the circuit through the differential winding of stepping magnet another circuit is also estab ished for cut-off relay 3 extending from grounded battery, winding of relay 10. brush 13,- and winding of relay 3, to ground. Relays 3 and 10 energize in this circuit and by at tracting its armatures relay 3 extends the calling line through brushes l4 and 15 to the seized trunk. In so doing the circuit for relay 2 is opened and this relay then releases. In attracting its armature relay i removes battery from the back contact and thus p events seizure of the selector switch by another line switch. After the calling line has been extended to the selector switch the subscriber at substation 1 may transmit sets of impulses to operate the succeeding switch or switches in any wc lhknown manner until the call is established. At any time thereafter means are providedl'or operating the register magnet 12. This means is )referably shown as consisting of a normally open key 16 which may be placed at an operators position and which, when depressed, will establish a circuit from a rounded battery of high potential. through iiey 16, front contact and armature of relay 10, brush 11 and winding of magnet 12, to ground.

The opcning in any well-known manner of the circuit for relay i l at the selector switch at the termination of the call. releases the relay together with cubofl' relay 3. 'hcn relay 3 releases the sclf-interrnpting circuit for magnet 4 extending from grounded battery at relay through brush t and contact ha i), wibl be established and thc switch will be returned to normal as previously described.

U11 incoming calls to substation 1. if the line is idle, a circuit will be established for cut'of'i' relay i'i-cxtcnding from ground,

through the winding of said relay, brush 13 and its normal contact, and conductor 7 to. battery at the final connector switch which has been set upon the terminals-of the line/ Relay 3 will energlze and, by attracting-its toniatic switch, a differentially wound stepping magnet for operating said switch. and means for energizing the windings of said magnet to prevent further operation thereof when the switch engages terminals of an idle line.

2. in a telephone exchange system, an au-i tomatic switch. a stepping magnet for the switch having a normally inactive difi'crcntial winding, a circuit for operating said magnet. undqneans for cncrgizing said differential winding to prevent operation of said magnet when the switch engages terminals of all-idle line.

3. In a telephone exchange system. an antomatic switch. a line relay therefor. a stepping rnagnct for said switch having a differential windin :1 circuit'f'or operating said stepping magnet extending through a contact of said line relay. and a second cir cuit extending through another contact of said line relay for energizing the differential winding of said step )ing magnet to stop the opcration thereof w N311 the switch en- ,gages terminals of an idleline.

4. In a telephone exchange system, an antomatic switch having a normal position. a line relay therefor. a stepping magnet for said switch having a differential winding. a circuit for operating said stepping magnet extending through a contact of said line rclav. a second circuit extending through an other contact of said linc relay for energir ing the differential winding of said stepping magnct to stop the dperation thereof" when the switch engages terminalsgof an idle line, and a third circuit independent of the contacts of said line relay for operatin said stepping magnet to return the switci to normal.

"In witness whereof, l hcrcunto subscribe my name this 4th day 0 igust, A. D. 1919.

GEORGE THOMPSON.

DIBCLAMER.

1,383,677.-George Thom ion, Mount Vernon,N. Y. Tnwrnonz-Excneaae SYS- TEM. Pinent dated uly 5, 1921. Disclaimer filed April 4, 1928, by the assignee,

Western blectric''ompany, Incorporated.

in the following wor'ds to wit:

nlereby enters this disciaimer to that part of the claims in said specification which 1. In a. telephone exchange system, an automatic switch, a difl'erentil'lly wound stepping mngnet for operating said switch, and means for energizinfi qfu 'aid magnet to pevent further operation thereof when the swite engages terminals of an idle line.

"2, In a telephone esehsn e system, an automatic switrh. a stepping magnet for the switch having a; no y inactive difierential Windin", a cijhiit for operating aid m t, and n eanafoi energizing snid'difleieptiul win ing to prevent operation a! said. egnet whegtfie switch engages terminals of an idle line."

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the windings 

